code: def test_theta(self):
      np.random.seed(1)
      series = rt(length=50, mean=100)
      theta_param = np.random.randint(1, 5)
      theta = Theta(theta_param)
      fourtheta = FourTheta(theta_param, normalization=False)
      theta.fit(series)
      fourtheta.fit(series)
      forecast_theta = theta.predict(20)
      forecast_fourtheta = fourtheta.predict(20)
      weighted_delta = (
          forecast_theta - forecast_fourtheta
      ) / forecast_theta
      assert (weighted_delta <= 3e-5).all().item()
  
file_path: darts/darts/tests/models/forecasting/test_4theta.py
imports: import random
  import numpy
  import pytest
  from darts.metrics import mape
  from darts.models import FourTheta, Theta
  from darts.utils.timeseries_generation import linear_timeseries
  from darts.utils.timeseries_generation import random_walk_timeseries
  from darts.utils.timeseries_generation import sine_timeseries
  from darts.utils.utils import ModelMode, SeasonalityMode, TrendMode
label_desc: Use image node_id 4 for calling the TestFourTheta obj's underlying member method code with example usage: obj.test_theta() without return types